Ureaplasma parvum causes hyperammonemia in a pharmacologically immunocompromised murine model

Minimizing the Risk of Donor-Derived Events and Maximizing Organ Utilization Through Education and Policy Development

Herein, we review the current knowledge of donor-derived disease and current US Organ Procurement and Transplantation Network policies to minimize the risk. During the process, we also consider actions to further mitigate the risk of donor-derived disease. The overarching goal is to provide an infectious disease perspective on the complex decision of organ acceptance for transplant programs and candidates.

Hyperammonaemia syndrome in disseminated Ureaplasma parvum infection

Hyperammonaemia syndrome secondary to Ureaplasma spp. infection is well documented in the post-lung transplant population. We report a case of a man in his fifties with hyperammonaemia syndrome secondary to disseminated Ureaplasma parvum infection. This occurred in the context of immunosuppression for chronic graft versus host disease and six years following an allogeneic stem cell transplant for diffuse large B-cell lymphoma. Following treatment of U. parvum septic arthritis with ciprofloxacin and doxycycline, the patient experienced a full neurological recovery, and continues on suppressive doxycycline therapy with no recurrence of symptoms to date.

Flurofamide Prevention and Treatment of Ureaplasma-Induced Hyperammonemia

Hyperammonemia (HA) syndrome caused by respiratory infection with ammonia (NH3)-producing Ureaplasma species occurs in 4% of lung transplant recipients (LTRs) and is associated with high mortality. Although Ureaplasma-targeted antibiotic intervention is effective, the threat of antibiotic resistance development and pre-existing resistance make an alternative to antibiotics desirable. Considering that the underlying pathology of Ureaplasma-induced hyperammonemia (UIHA) is dependent upon ureaplasmal urease converting urea to NH3, urease inhibition could represent a targeted treatment approach. Here, the ability of the urease inhibitor, flurofamide, to prevent and treat UIHA was investigated. To confirm that flurofamide is broadly active against Ureaplasma respiratory isolates, the minimum urease inhibitory concentration against 4 isolates of Ureaplasma parvum and 5 isolates of Ureaplasma urealyticum was first determined in vitro. NH3 production by all isolates was inhibited by ≤2 μM flurofamide. To test the ability of flurofamide to prevent and treat UIHA, a mouse model of Ureaplasma respiratory infection was utilized. When animals were administered 6 mg/kg flurofamide via intraperitoneal injection 1 h prior to infection with U. parvum, flurofamide-administered animals exhibited significantly lower blood NH3 levels than did non-prophylaxed animals (10.9 ± 4.0 μmol/L compared to 26.5 ± 17.7 μmol/L; P = 0.0146) 24 h post-treatment. When U. parvum-infected hyperammonemic mice were treated with 6 mg/kg flurofamide, treated animals had significantly greater decreases in blood-NH3 levels 6 h post-treatment than did untreated mice (56.4 ± 17.1% compared to 9.1 ± 33.5% reduction; P = 0.0152). Together, these results indicate that flurofamide is a promising non-antibiotic treatment for UIHA in LTRs. IMPORTANCE Ureaplasma-associated hyperammonemia syndrome occurs in 4% of lung transplant recipients and has historically been almost universally fatal. While Ureaplasma-targeted antibiotics have been shown to be protective, the possibility of underlying resistance and resistance selection render non-antibiotic interventions an interesting approach.

Hyperammonemia syndrome in immunosuppressed individuals

PURPOSE OF REVIEW

Hyperammonemia syndrome is an increasingly recognized and often fatal condition that occurs in immunosuppressed individuals, most commonly lung transplant recipients. Growing evidence suggests hyperammonemia syndrome is associated with systemic infections caused by urease-producing organisms, namely Ureaplasma spp., an organism unable to grow with routine culturing techniques. This review will summarize the epidemiology and clinical manifestations of hyperammonemia syndrome, as well as diagnostic and management strategies once hyperammonemia syndrome is suspected.

RECENT FINDINGS

Hyperammonemia syndrome is being described in increasing frequency in the solid organ transplant population. Morbidity and mortality, even with treatment, is high once hyperammonemia syndrome occurs. Surveillance studies indicate the prevalence of lung donor colonization with Ureaplasma spp. is high, suggesting screening and treatment may be of benefit. Antibiotic resistance is common, and rapid diagnostics can facilitate appropriate antimicrobial therapy in the peri-transplant period.

SUMMARY

Hyperammonemia syndrome is most commonly seen in lung transplant recipients and has a high mortality rate once it occurs. Screening for Ureaplasma spp. should be considered in all lung transplant donors.

Diagnosis of Ureaplasma parvum meningitis by mNGS in an extremely low birth weight infant with multi-system lesions

Ureaplasma parvum encephalitis is a rare disease with high mortality in the neonates. While the manifestations are atypical and identification of U. parvum is difficult, diagnosis would always be delayed. Metagenomic next-generation sequencing (mNGS) is a pre-hypothesis free technique which could theoretically detect all the microbes in a sample. Herein we report a case of U. parvum meningitis identified by mNGS in an extremely low birth weight neonate complicated with multi-system lesions. The patient was treated with erythromycin and ciprofloxacin, symptoms were relieved in the following days and the patient was transferred to treat complications after three weeks' therapy.

Hyperammonemia After Lung Transplantation: Systematic Review and a Mini Case Series

Background: Hyperammonemia after lung transplantation (HALT) is a rare but serious complication with high mortality. This systematic review delineates possible etiologies of HALT and highlights successful strategies used to manage this fatal complication.

Methods: Seven biomedical databases and grey literature sources were searched using keywords relevant to hyperammonemia and lung transplantation for publications between 1995 and 2020. Additionally, we retrospectively analyzed HALT cases managed at our institution between January 2016 and August 2018.

Results: The systematic review resulted in 18 studies with 40 individual cases. The mean peak ammonia level was 769 μmol/L at a mean of 14.1 days post-transplant. The mortality due to HALT was 57.5%. In our cohort of 120 lung transplants performed, four cases of HALT were identified. The mean peak ammonia level was 180.5 μmol/L at a mean of 11 days after transplantation. HALT in all four patients was successfully treated using a multimodal approach with an overall mortality of 25%.

Conclusion: The incidence of HALT (3.3%) in our institution is comparable to prior reports. Nonetheless, ammonia levels in our cohort were not as high as previously reported and peaked earlier. We attributed these significant differences to early recognition and prompt institution of multimodal treatment approach.

Contribution of Uremia to Ureaplasma-Induced Hyperammonemia

Lung transplant recipients (LTRs) are vulnerable to hyperammonemia syndrome (HS) in the early postoperative period, a condition typically unresponsive to nonantibiotic interventions. HS in LTRs is strongly correlated with Ureaplasma infection of the respiratory tract, although it is not well understood what makes LTRs preferentially susceptible to HS compared to other immunocompromised hosts. Ureaplasma species harbor highly active ureases, and postoperative LTRs commonly experience uremia. We hypothesized that uremia could be a potentiating comorbidity, providing increased substrate for ureaplasmal ureases. Using a novel dialyzed flow system, the ammonia-producing capacities of four isolates of Ureaplasma parvum and six isolates of Ureaplasma urealyticum in media formulations relating to normal and uremic host conditions were tested. For all isolates, growth under simulated uremic conditions resulted in increased ammonia production over 24 h, despite similar endpoint bacterial quantities. Further, transcripts of ureC (from the ureaplasmal urease gene cluster) from U. urealyticum IDRL-10763 and ATCC-27816 rose at similar rates under uremic and nonuremic conditions, with similar endpoint populations under the two conditions (despite markedly increased ammonia concentrations under uremic conditions), indicating that the difference in ammonia production by these isolates is due to increased urease activity, not expression. Lastly, uremic mice infected with an Escherichia coli strain harboring a U. urealyticum serovar 8 gene cluster exhibited higher blood ammonia levels compared to nonuremic mice infected with the same strain. Taken together, these data show that U. urealyticum and U. parvum produce more ammonia under uremic conditions compared to nonuremic conditions. This implies that uremia is a plausible contributing factor to Ureaplasma-induced HS in LTRs. IMPORTANCE Ureaplasma-induced hyperammonemia syndrome is a deadly complication affecting around 4% of lung transplant recipients and, to a lesser extent, other solid organ transplant patients. Understanding the underlying mechanisms will inform patient management, potentially decreasing mortality and morbidity. Here, it is shown that uremia is a plausible contributing factor to the pathophysiology of the condition.

Review: immunosuppression for the lung transplant patient

Lung transplantation (LTx) has evolved significantly since its inception and the improvement in LTx outcomes over the last three decades has predominantly been driven by advances in immunosuppression management. Despite the lack of new classes of immunosuppression medications, immunosuppressive strategies have evolved significantly from a universal method to a more targeted approach, reflecting a greater understanding of the need for individualized therapy and careful consideration of all factors that are influenced by immunosuppression choice. This has become increasingly important as the demographics of lung transplant recipients have changed over time, with older and more medically complex candidates being accepted and undergoing LTx. Furthermore, improved survival post lung transplant has translated into more immunosuppression related comorbidities long-term, predominantly chronic kidney disease (CKD) and malignancy, which has required further nuanced management approaches. This review provides an update on current traditional lung transplant immunosuppression strategies, with modifications based on pre-existing recipient factors and comorbidities, peri-operative challenges and long term complications, balanced against the perpetual challenge of chronic lung allograft dysfunction (CLAD). As we continue to explore and understand the complexity of LTx immunology and the interplay of different factors, immunosuppression strategies will require ongoing critical evaluation and personalization in order to continue to improve lung transplant outcomes.

Ureaplasma parvum meningitis following atypical choroid plexus papilloma resection in an adult patient: a case report and literature review

Background

While Ureaplasma parvum has previously been linked to the incidence of chorioamnionitis, abortion, premature birth, and perinatal complications, there have only been rare reports of invasive infections of the central nervous system (CNS) in adults. Owing to its atypical presentation and the fact that it will yield sterile cultures using conventional techniques, diagnosing U. parvum meningitis can be challenging.

Case presentation

We describe a case of U. parvum meningitis detected in an adult patient following surgical brain tumor ablation. After operation, the patient experienced epilepsy, meningeal irritation, and fever with unconsciousness. Cerebrospinal fluid (CSF) analysis showed leukocytosis (484 * 10⁶ /L), elevated protein levels (1.92 g/L), and decreased glucose concentrations (0.02 mmol/L). Evidence suggested that the patient was suffering from bacterial meningitis. However, no bacterial pathogens in either CSF or blood were detected by routine culture or serology. The symptoms did not improve with empirical antibiotics. Therefore, we performed metagenomic next-generation sequencing (mNGS) to identify the etiology of the meningitis. Ureaplasma parvum was detected by mNGS in CSF samples. To the best of our knowledge, this case is the first reported instance of U. parvum meningitis in an adult patient in Asian. After diagnosis, the patient underwent successful moxifloxacin treatment and recovered without complications.

Conclusions

As mNGS strategies can enable the simultaneous detection of a diverse array of microbes in a single analysis, they may represent a valuable means of diagnosing the pathogens responsible for CNS infections and other clinical conditions with atypical presentations.

Hyperammonemia syndrome associated with Ureaplasma spp. Infections in immunocompromised patients and transplant recipients: A systematic review and meta-analysis

BACKGROUND

Hyperammonemia syndrome (HS) is reported to occur in patients with Ureaplasma spp. infections. We performed a systematic review and meta-analysis of studies reporting HS in patients with Ureaplasma spp. infection.

METHODS

We searched several databases (CINAHL, OVID, ProQuest, and Scopus) from inception to January 2021. We described case reports and series, and performed a meta-analysis for all cohort studies. The pooled risk ratio (RR) for the association between HS and Ureaplasma spp. infections was derived using a random-effects model.

RESULTS

The systematic review yielded 18 studies. HS was reported in 53 patients with Ureaplasma spp. infections. The most common clinical manifestations were neurologic. Meta-analysis showed a higher incidence of HS (41.67%) and peak ammonia concentration among Ureaplasma spp.-infected lung transplant recipients compared with Ureaplasma spp.-negative recipients (2.84%). The risk of HS was significantly increased in Ureaplasma spp.-infected recipients compared with Ureaplasma spp.-negative recipients (RR: 14.64; CI: 2.85-75.24). Mortality from Ureaplasma-associated HS was 27.27% compared with 5.24% in those with HS from other causes.

CONCLUSIONS

The risk of developing HS is higher among Ureaplasma-infected patients compared with uninfected patients. Lung transplant recipients appear to be disproportionally affected, and HS should be suspected in those who present with neurologic symptoms.

A novel bioreactor for the stable growth of Ureaplasma parvum and Ureaplasma urealyticum

Ureaplasma species, including Ureaplasma parvum and Ureaplasma urealyticum, are challenging to culture and maintain. Here, we describe a novel bioreactor for growing high-titer liquid Ureaplasma cultures in a stable manner.

Hyperammonemia Post Lung Transplantation: A Review

Hyperammonemia is the pathological accumulation of ammonia in the blood, which can occur in many different clinical settings. Most commonly in adults, hyperammonemia occurs secondary to hepatic dysfunction; however, it is also known to be associated with other pathologies, surgeries, and medications. Although less common, hyperammonemia has been described as a rare, but consistent complication of solid organ transplantation. Lung transplantation is increasingly recognized as a unique risk factor for the development of this condition, which can pose grave health risks-including long-term neurological sequelae and even death. Recent clinical findings have suggested that patients receiving lung transplantations may experience postoperative hyperammonemia at rates as high as 4.1%. A wide array of etiologies has been attributed to this condition. A growing number of case studies and investigations suggest disseminated opportunistic infection with Ureaplasma or Mycoplasma species may drive this metabolic disturbance in lung transplant recipients. Regardless of the etiology, hyperammonemia presents a severe clinical problem with reported mortality rates as high as 75%. Typical treatment regimens are multimodal and focus on 3 main avenues of management: (1) the reduction of impact on the brain through the use of neuroprotective medications and decreasing cerebral edema, (2) augmentation of mechanisms for the elimination of ammonia from the blood via hemodialysis, and (3) the diminishment of processes producing predominantly using antibiotics. The aim of this review is to detail the pathophysiology of hyperammonemia in the setting of orthotopic lung transplantation and discuss methods of identifying and managing patients with this condition.

Impact of Screening and Treatment of Ureaplasma spp on Hyperammonemia Syndrome in Lung Transplant Recipients: A Single Center Experience

BACKGROUND

Infection with Ureaplasma species (spp) has been linked to fatal hyperammonemia syndrome (HS) in lung transplant recipients. We sought to characterize the epidemiology of Ureaplasma spp in candidates and donors and describe outcomes of antimicrobial therapy in preventing and treating HS.

METHODS

Candidate testing for Ureaplasma spp was performed with urine culture and PCR pre-transplant. Positive candidates were treated with levofloxacin. Donor testing was performed with bronchoalveolar lavage culture and PCR intraoperatively. From 7/2014-2/2017 patients were treated according to results; from 2/2017-10/2018 recipients received empiric levofloxacin and azithromycin at transplant until testing returned negative. HS was defined as new onset altered mental status after transplant with ammonia > 200 µmol/L.

RESULTS

60 patients who underwent lung transplant were included. 80% (n = 48) of patients had negative screening tests in donor and candidate pre-lung transplant, 8.3% (n = 5) of recipients had positive Ureaplasma spp testing in urine pre-transplant, and 13.3% (n = 8) had positive donor BAL testing at the time of lung transplant. 3 patients developed HS a median of 7 days post-transplant; 2 died of HS. Recipients of organs with Ureaplasma spp who received empiric therapy did not develop HS. Donors with Ureaplasma spp were younger and more sexually active.

CONCLUSION

Donor-derived Ureaplasma spp in lung transplant was associated with HS. Screening lung donors for Ureaplasma spp might allow for targeted therapy to reduce risk for development of HS, but future confirmatory studies are needed.

Hyperammonemia syndrome due to Ureaplasma infection after liver-kidney transplant

Hyperammonemia syndrome, with high levels of ammonia and neurologic dysfunction, is a syndrome with historically high mortality that may occur after solid organ transplantation. Recently, this has been associated with infection due to Ureaplasma, mostly following lung transplantation. We describe the first case of hyperammonemia syndrome due to Ureaplasma infection after liver-kidney transplantation. Our patient rapidly recovered after specific antibiotic treatment. It is important to consider these infections in the differential diagnosis for encephalopathy post-transplant, as these organisms often do not grow using routine culture methods and polymerase chain reaction testing is typically required for their detection. This is particularly critical after liver transplantation, where a number of other etiologies may be considered as a cause of hyperammonemia syndrome.

Neonatal Ureaplasma parvum meningitis: a case report and literature review

Ureaplasma parvum (U. parvum) is common commensal in the female genitourinary tract. Despite U. parvum has been associated with chorioamnionitis, abortion, prematurity and perinatal complications, the invasive central nervous system (CNS) infection is rare in neonates. Diagnosis of U. parvum meningitis can be difficult for the atypical presentations and sterile cultures by conventional methods. Metagenomic next-generation sequencing (mNGS) could identify a broad range of human pathogens in a target-independent manner. Here, we performed mNGS to search for the infectious etiology in a term infant presenting with fever and seizure. U. parvum genome was identified by mNGS and further confirmed by PCR in the same cerebrospinal fluid (CSF) sample. As the quick and timely diagnosis, the baby was successfully treated with erythromycin for 4 weeks without complication. The clinical follow-up has showed that the physical and mental development are normal. In conclusion, mNGS may a promising diagnostic technology for U. parvum meningitis. As mNGS is able to identify diverse microbes in a single run, it could be a useful strategy to detection the clinical causative pathogens with atypical features in neonates.

Hyperammonemia From Ureaplasma Infection in an Immunocompromised Child

Idiopathic hyperammonemia is a rare, poorly understood, and often lethal condition that has been described in immunocompromised patients. This report describes an immunocompromised patient with acute myelogenous leukemia who developed persistent hyperammonemia up to 705 µmol/L (normal, 0 to 47 µmol/L) refractory to multiple different therapies. However, after beginning azithromycin and then doxycycline therapy for Ureaplasma species infection, the patient showed immediate and sustained clinical improvement and resolution of ammonia levels. Recognizing disseminated Ureaplasma species infection as a potential cause of idiopathic hyperammonemia, an unexplained, often fatal condition in immunocompromised patients, and empirically treating for this infection could potentially be lifesaving.

Ureaplasma parvum causes hyperammonemia presenting as refractory status epilepticus after kidney transplant

PURPOSE

Alert intensivists about the diagnostic pitfalls arising from hyperammonemia due to Ureaplasma infections in post-transplant patients.

MATERIALS AND METHODS

Clinical observation of one patient.

CASE REPORT

A 65-year-old female with a medical history of semi-recent kidney transplant was admitted to the Intensive Care Unit for refractory status epilepticus. There were no lesions on brain imaging. Bacterial cultures and viral PCR of cerebrospinal fluid were negative. The first blood ammonia level measured on day 2 was 13 times the normal level, but biological liver tests were normal. The persistence of elevated ammonia levels led to the initiation of symptomatic ammonia lowering-treatments and continuous renal replacement therapy, which led to its decrease without normalization. An Ureaplasma spp infection was then diagnosed. Levofloxacin and doxycyline were administered resulting in normalization of ammonia levels within 48 h. However repeat MRI showed diffuse cortical cytotoxic edema and the patient remained in a minimally conscious state. She eventually died 4 months later from a recurrent infection.

CONCLUSION

Ureaplasma infection must be suspected in cases of neurological symptoms associated with hyperammonemia without liver failure, following an organ transplant. Only urgent treatment could improve the prognosis and prevent severe neurological damage or death.

An Update in Antimicrobial Therapies and Infection Prevention in Pediatric Lung Transplant Recipients

Lung transplantation can offer life-prolonging therapy to children with otherwise terminal end-stage lung disease. However, infectious complications, like those experienced by their adult counterparts, are a significant cause of morbidity and mortality. These include bacteria, viruses, and fungi that infect the patient pretransplant and those that may be acquired from the donor or by the recipient in the months to years posttransplant. An understanding of the approach to the management of each potential infecting organism is required to ensure optimal outcomes. In particular, emphasis on aggressive preoperative management of infections in pediatric patients with cystic fibrosis is important. These include multidrug-resistant Gram-negative bacteria, fungi, and Mycobacterium abscessus, the posttransplant outcome of which depends on optimal pretransplant management, including vaccination and other preventive, antibiotic-sparing strategies. Similarly, increasing the transplant donor pool to meet rising transplant demands is an issue of critical importance. Expanded-criteria donors-those at increased risk of blood-borne viruses in particular-are increasingly being considered and transplants undertaken to meet the rising demand. There is growing evidence in the adult pool that these transplants are safe and associated with comparable outcomes. Pediatric transplanters are therefore likely to be presented with increased-risk donors for their patients. Finally, numerous novel antibiotic-sparing therapeutic approaches are on the horizon to help combat infections that currently compromise transplant outcomes.

Successful treatment of Ureaplasma-induced hyperammonemia syndrome post-lung transplant

Hyperammonemia, in the absence of significant liver dysfunction, is an uncommon but often fatal occurrence following orthotopic lung transplant. Prior reports have provided evidence to support Ureaplasma species as an etiology for this syndrome. This case report describes an individual post-lung transplant, treated emperically with doxycycline along with other measures to lower ammonia levels, at the time hyperammonemia with encephalopathy was recognized. The patient clinically improved. Ureaplasma species were subsequently identified using 16S ribosomal RNA gene PCR/sequencing of pleural fluid, and by culture of bronchoalveolar (BAL) fluid. This case provides further support for empiric treatment of Ureaplasma species upon recognition of hyperammonemia syndrome post-lung transplant.

Successful resolution of hyperammonemia following hematopoietic cell transplantation with directed treatment of Ureaplasma parvum infection

Hyperammonemia following hematopoietic cell transplantation (HCT) has been characterized as idiopathic and is associated with a very high mortality. A causal relationship between Ureaplasma infection and hyperammonemia in immunocompromised lung transplant recipients has recently been described. We document the first case of hyperammonemia following HCT associated with Ureaplasma parvum. The initiation of appropriate antibiotics resulted in rapid resolution of hyperammonemic encephalopathy and eradication of the implicating organism.